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NAME

     sighold, sigignore, sigpause, sigrelse, sigset -- legacy interface for
     signal management

LIBRARY

     Standard C Library (libc, -lc)

SYNOPSIS

     #include <signal.h>

     int
     sighold(int sig);

     int
     sigignore(int sig);

     int
     xsi_sigpause(int sigmask);

     int
     sigrelse(int sig);

     void (*)(int)
     sigset(int, void (*disp)(int));

     int
     sigpause(int sigmask);

DESCRIPTION

     This interface is made obsolete by sigsuspend(2) and sigaction(2)

     The sigset() function modifies signal dispositions.  The sig argument
     specifies the signal, which may be any signal except SIGKILL and SIGSTOP.
     The disp argument specifies the signal's disposition, which may be
     SIG_DFL, SIG_IGN, or the address of a signal handler.  If sigset() is
     used, and disp is the address of a signal handler, the system adds sig to
     the signal mask of the calling process before executing the signal
     handler; when the signal handler returns, the system restores the signal
     mask of the calling process to its state prior to the delivery of the
     signal.  In addition, if sigset() is used, and disp is equal to SIG_HOLD,
     sig is added to the signal mask of the calling process and sig 's
     disposition remains unchanged.  If sigset() is used, and disp is not
     equal to SIG_HOLD, sig is removed from the signal mask of the calling
     process.

     The sighold() function adds sig to the signal mask of the calling
     process.

     The sigrelse() function removes sig from the signal mask of the calling
     process.

     The sigignore() function sets the disposition of sig to SIG_IGN.

     The xsi_sigpause() function removes sig from the signal mask of the
     calling process and suspend the calling process until a signal is
     received.  The xsi_sigpause() function restores the signal mask of the
     process to its original state before returning.

     The sigpause() function assigns sigmask to the set of masked signals and
     then waits for a signal to arrive; on return the set of masked signals is
     restored.  The sigmask argument is usually 0 to indicate that no signals
     are to be blocked.

RETURN VALUES

     The sigpause() and xsi_sigpause() functions always terminate by being
     interrupted, returning -1 with errno set to EINTR.

     Upon successful completion, sigset() returns SIG_HOLD if the signal had
     been blocked and the signal's previous disposition if it had not been
     blocked.  Otherwise, SIG_ERR is returned and errno set to indicate the
     error.

     For all other functions, upon successful completion, 0 is returned.
     Otherwise, -1 is returned and errno is set to indicate the error:

     [EINVAL]           The sig argument is not a valid signal number.

     [EINVAL]           For sigset() and sigignore() functions, an attempt was
                        made to catch or ignore SIGKILL or SIGSTOP.

SEE ALSO

     kill(2), sigaction(2), sigblock(2), sigprocmask(2), sigsuspend(2),
     sigvec(2)

STANDARDS

     The sigpause() function is implemented for compatibility with historic
     4.3BSD applications.  An incompatible interface by the same name, which
     used a single signal number rather than a mask, was present in AT&T
     System V UNIX, and was copied from there into the X/Open System
     Interfaces (XSI) option of IEEE Std 1003.1-2001 (``POSIX.1'').  FreeBSD
     implements it under the name xsi_sigpause().  The sighold(), sigignore(),
     sigrelse() and sigset() functions are implemented for compatibility with
     System V and XSI interfaces.

HISTORY

     The sigpause() function appeared in 4.2BSD and has been deprecated.  All
     other functions appeared in FreeBSD 8.1 and were deprecated before being
     implemented.